Regeneration and colonization abilities of aquatic plant fragments: effect of disturbance seasonality

The regeneration (regrowth into viable plants or production of propagules, such as turions or buds) and colonization (development of roots and establishment in the sediment) of fragments of six aquatic plant species (Elodea canadensis Michaux, Hippuris vulgaris L., Luronium natans (L.) Rafin., Potamogeton pusillus L., Ranunculus trichophyllus Chaix, Sparganium emersumRehmann) occurring in habitats frequently disturbed by floods, were investigated through laboratory experiments conducted in two seasons, and compared to the recolonization patterns depicted after field experiments. Hypothesis was that differences observed between recolonization patterns after spring and autumn flood disturbances should be related to differences in recolonization (via rooting) and regeneration (via propagules) abilities of species fragments. In May and in August, five types of fragments were collected from the plants. Their development and/or rooting abilities were recorded over 10 weeks in the greenhouse. Fragments from E. canadensisand H. vulgarishad higher regeneration and lower colonization abilities in spring and conversely in autumn. Fragments from R. trichophyllusand S. emersumhad high colonization and low regeneration abilities during both seasons. Fragments from L. natans developed new buds in spring, whereas root development occurred only in autumn. Fragments from P. pusillus never rooted into the sediment, but developed turions in autumn. Differences between recolonization patterns observed in the field at the two seasons can most often be related to differences in regeneration and colonization abilities of species fragments. Species that colonize disturbed areas rapidly whenever the disturbance by flooding occurs have at least one type of vegetative fragment with a high colonization potential; this is called the `always-ready strategy' which appears to be an adaptation of aquatic plants to the unpredictability of flood disturbances.     

Being evergreen in an aquatic habitat with attenuated seasonal contrasts – a major competitive advantage?

This study experimentally compares growth of four aquatic macrophytes species (Sparganium emersum Rehm., Hippuris vulgaris L., Groenlandia densa (L.) Fourr., Luronium natans (L.) Raf.) with different modes of winter persistence in a thermally buffered habitat. The question is whether the above-ground persistence of photosynthetic structures during winter can compensate for low growth rates of evergreens when they compete with fast growing, non-evergreen species. The experiment was carried out in experimental boxes installed in a former river channel fed by stenothermic ground-water. Species were planted pairwise in experimental boxes in autumn, monitoring was carried out in the following year: degree of evergreenness was evaluated through number of ramets present prior to the main growing season, competitive ability of species was assessed during the growing season through cover measurements at three dates. Degree of evergreenness varied considerably between species, ranging from increase of ramet numbers during winter in Luronium over preservation of ramet numbers in Groenlandia and Hippuris to nearly complete winter die-back in Sparganium. Luronium presented the highest cover during the entire growing season. Only by the end of summer did Sparganium attain a similar cover through a high growth rate. Despite large differences in cover, growth appeared largely unaffected by the kind of treatment partner a species was confronted with. Nevertheless, this study demonstrates that being evergreen can compensate for a low growth rate during the main growing season when it is associated to extensive growth outside this main growing season.     

Introduction of Nonindigenous Aquatic Vascular Plants in Southern New England: A Historical Perspective

Aquatic plants comprise few species worldwide, yet introductions of nonindigenous hydrophytes represent some of the most severe examples of biological invasions. Often innocuous in their indigenous regions, many aquatic plant species have caused extreme ecological and economic consequences when introduced into nonindigenous habitats. Typically, aquatic plant invasions are unnoticed or overlooked until they are perceived as problematic. By then, plants are virtually impossible to eradicate and negative ecological impacts caused by their spread into natural communities are irreparable. We present criteria to facilitate decisions whether a species should be characterized as nonindigenous or invasive. Historical data are used to clarify methods of introduction, avenues and means of dispersal, and extent of invasiveness of the following aquatic plants in southern New England: Acorus calamus, Butomus umbellatus, Cabomba caroliniana, Callitriche stagnalis, Egeria densa, Hydrilla verticillata, Limnobium spongia, Marsilea quadrifolia, Myriophyllum aquaticum, Myriophyllum heterophyllum, Myriophyllum spicatum, Najas minor, Najas guadalupensis, Nasturtium officinale, Nymphoides peltata, Potamogeton crispus, Trapa natans and Veronica beccabunga.     

Photon-harvesting efficiency and arbuscular mycorrhiza in amphibious plants

The amphibious plant species of intermittent aquatic habitats thrive both submerged and emerged. In order to outline the adaptive characters of these two life forms photochemical efficiency of photosystem 2, leaf contents of chlorophyll (Chl) a and b, carotenoids (Car), anthocyanins (Ant), and UV-B absorbing compounds (UV-B abs), and root aerenchyma and arbuscular mycorrhizal (AM) colonisation were studied in Glyceria fluitans, Gratiola officinalis, Ranunculus lingua, Teucrium scordium, Sium latifolium, Sparganium emersum, and Veronica anagallis-aquatica. Water level fluctuations did not exert a severe effect on photon harvesting efficiency. Submerged specimens had higher contents of Car and Ant whereas higher contents of UV-B abs were found in emerged specimens indicating efficient protection against the harmful effects of solar radiation. Roots of all species studied had extensive aerenchyma and were colonised by AM fungi, which were significantly more abundant in emerged specimens. This is the first report on AM symbiosis in S. latifolium and S. emersum.     

Habitat and sex specific differences in the dioecious weed Acetosella vulgaris (Polygonaceae)

Abstract Patterns of resource allocation, numbers of reproductive structures and sex ratios of flowering populations of the dioecious weed Acetosella vulgaris (Fourr.) were examined in the Kosciuszko alpine region of Australia. Specifically, the sex‐specific response of ramets was compared between a disturbed alpine habitat, in which weeds such as A. vulgaris are common (disturbed roadside/path‐edge), and a native alpine habitat in which weeds appear to have a limited capacity to germinate, grow and reproduce (undisturbed tall alpine herbfield). The disturbed habitat was generally more favourable for growth of A. vulgaris. Ramets of both sexes had greater total and vegetative biomass than ramets in native habitats. Although reproductive biomass was also greater in disturbed habitats, females had less reproductive biomass than males, which was not as predicted. Reproductive effort was not affected by habitat or gender. The disturbed habitat also favoured increased numbers of inflorescences per ramet and flowers per ramet, as expected. Whereas the gender of the ramet also influenced numbers of reproductive structures, again, this was not as predicted. Females had more flowers per ramet and more flowers per inflorescence than males. This may be because of factors associated with wind pollination. Females were taller in native habitats but there was no difference between the sexes in disturbed habitats. Sex ratios varied from all male populations to nearly all female populations among the 25 sites sampled irrespective of habitat. Factors such as time since last disturbance may have contributed to variation in the sex ratios of alpine populations of A. vulgaris in Australia.     

Persistence of a rare aquatic species along gradients of disturbance and sediment richness

Abstract. This study examines the capacity of establishment of a rare aquatic macrophyte, Luronium natans, within plant communities and habitat types in which it does not occur spontaneously. The species, generally limited to disturbed or nutrient‐poor habitats, was transplanted into a series of sites situated along natural gradients of disturbance (flush‐floods and intermittent sediment exposure) and sediment nutrient‐richness. The transplanted colonies were given a competition‐free establishment period. Colony dynamics of Luronium as well as size structure of the recolonizing macrophyte communities were monitored over three growing seasons. At the end of this period, transplanted colonies still persisted in five out of 12 transplantation sites. Apparently successful integration into the community occurred at both ends of the nutrient gradient, in periodically disturbed habitats. At intermediate to high nutrient richness Luronium maintained one of the highest cover values within the recolonizing community. The study supports previous presumptions that long‐term persistence of Luronium depends on processes limiting community biomass through occurrence of disturbance. But it also reveals the existence of suitable, yet not occupied habitats in which the species can persist as successfully as species from the local species pool. This finding modulates the presumption that Luronium's rarity is mainly caused by a weak competitive ability in the established phase. It thus rises questions about the species’ performance at other stages of its life cycle and on its dispersability.     

Habitat use of the European mudminnow Umbra krameri and association with other fish species in a disconnected Danube side arm

Fish assemblages along the longitudinal course of an old, disconnected and modified side arm of the Danube floodplain downstream of Vienna, Austria, as well as habitat structure, hydro‐morphological and hydro‐chemical factors, were investigated in order to analyse the key environmental determinants of the European mudminnow Umbra krameri. Generally, U. krameri was the most abundant species in the system. It occurred in disconnected ditches, ponds and pools with dense reed belts and comparatively low nutrient content, indicating its natural association with marsh habitats. At infrequently disturbed sites it was associated with a small group of stagnophilious and highly specialized species with adaptations to strong oxygen fluctuations. At frequently flooded sites, the species was absent or occurred in low abundances, indicating its adaptation to water bodies in older successional stages and its low competitive power in permanently connected floodplain habitats.     

A phytosociological study of the macrophytic vegetation of running waters in western lower saxony (Federal Republic of Germany)

A survey was carried out of the macrophytic vegetation in running waters of Western Lower Saxony. Three hundred and eighty-two phytosociological relevées were classified by common table work to 30 vegetation types of different phytosociological validity. The vegetation types are described and floristically characterized. Most of them belong to the complex Sparganium emersum community, which is characterized by the dominant occurrence of the nymphaeid species Sparganium emersum Rehm., Nuphar lutea (L.) Sm., Sagittaria sagittifolia L. and Potamogeton natans L., but magnopotamid-, parvopotamid-, batrachiid- and pleustophyte-dominated communities also occur. Similarity between the different vegetation types was checked by multivariate techniques, one classification technique (minimum variance clustering) and one ordination technique (principal components analysis). Additionally, syndynamical relations between the types were studied by observing the vegetation changes of 46 sample points within 2 years. The relations between different vegetation types are shown by combination of the different approaches. Finally, some more general statements are made regarding the handling of such data sets, as well as the consequences of the results for the classification of macrophytic vegetation in Central European rivers.     

水陆生境和氮沉降对香菇草(Hydrocotyle vulgaris)入侵湿地植物群落的影响

大气氮沉降对湿地外来植物入侵的影响已成为生态学研究的热点之一。选用梭鱼草(Pontederia cordata)、水菖蒲(Acorus calamus)、黄花鸢尾(Iris wilsonii)和粉绿狐尾藻(Myriophyllum aquaticum)模拟湿地植物群落,设置有无香菇草入侵、水生和陆生生境(水位分别为15 cm和0 cm)及有无氮沉降处理(15 g N m~(-2)a(-1)和0)交叉组成的8种处理组合,进行为期70d的温室控制实验,以分析水陆生境及氮沉降对香菇草入侵湿地植物群落的影响。结果表明:(1)水生生境下,香菇草的总生物量、叶生物量、叶片数和节点数与陆生生境相比显著降低;水生生境下氮沉降处理对香菇草各指标无显著影响,陆生生境下氮沉降处理的香菇草叶片数、节点数显著多于无氮沉降处理。(2)实验周期内氮沉降和香菇草入侵没有对群落的多样性指数及群落内4种湿地植物的生物量产生显著影响;水生生境下植物群落的总生物量及梭鱼草和粉绿狐尾藻的生物量与陆生生境相比显著提高。(3)水生生境下香菇草的相对优势度相比陆生生境下显著下降;氮沉降只在陆生生境下显著提高了香菇草的相对优势度。因此,香菇草向水生生境扩散和入侵的能力不强,其入侵在短时间内对湿地植物群落影响较小。研究结果可以为入侵植物生态学研究提供案例借鉴。     

Effects of Spirogyra arcta on biomass and structure of submerged macrophyte communities

The presence of algae can greatly reduce the amount of light that reaches submerged macrophytes, but few experimental studies have been conducted to examine the effects of algae on biomass and structure of submerged macrophyte communities. We constructed communities with four submerged macrophytes (Hydrilla verticillata, Egeria densa, Ceratophyllum demersum, and Chara vulgaris) in three environments in which 0 (control), 50 and 100% of the water surface was covered by Spirogyra arcta. Compared to the control treatment, the 100% spirogyra treatment decreased biomass of the submerged macrophyte communities and of all the four macrophytes except C. demersum. Compared to the control and 50% treatments, the 100% treatment significantly increased relative abundance of C. demersum and decreased that of E. densa. Therefore, the presence of S. arcta can greatly affect the productivity and alter the structure of submerged macrophyte communities. To restore submerged macrophyte communities in conditions with abundant algae, assembling communities consisting of C. demersum or similar species may be a good practice.     

Recolonization of cleared riverine macrophyte patches: importance of the border effect

Abstract. Recolonization of two experimentally cleared 9 m²-patches by macrophytes in a former channel of the Rhône River, France, was investigated from May to July 1994. Two patterns of recolonization were recognized: (1) Groenlandia densa, Luronium natans and Potamogeton natans invaded the bare areas by propagation from the adjacent vegetation (border effect); (2) Potamogeton pusillus colonized the disturbed areas at random, apparently independently from the position of nearby clumps. An intermediate recolonization pattern was shown by Callitriche platycarpa, Elodea canadensis, Hippuris vulgaris, Ranunculus circinatus and Sparganium emersum. Species recolonization patterns and associated strategies were related to species traits, particularly vegetative and sexual reproduction.     

Habitat conditions of the phytocoenoses dominated by Luronium natans (L.) Rafin in Poland

Phytosociological and habitat studies of the phytocoenoses of Luronium natans have been conducted. The present results were compared with data on L. dortmanna and I. lacustris. It is demonstrated that the community of L. natans differs from the other two communities with respect to habitat conditions despite the fact that they have been reported to occur jointly and alongside in Lobelia lakes. It appears that significant differences between the communities are found not only regarding their waters, but also their substrates. L. natans dominated phytocoenoses are confined to oligotrophic, extremely soft waters, markedly poor in Ca²⁺, but richer in Na⁺ and SO₄ ^2- than those of Lobelia and Isoëtes. Luronium natans develops best on acidic, highly hydrated substrates rich in organic matter, NO₃ ^– and total N. The results obtained indicate that L. natans and the phytocoenoses formed by it are characterized by their narrow ecological amplitude in Poland as opposed to those occurring in western Europe, which tolerate a relatively wide range of habitats. The present findings confirm the data from numerous works, which point to the weak competitive ability of the species compared with species typical of eutrophic waters.     

Relationships of hydrology and life-history strategies on the spatio-temporal habitat utilisation of fish in European temperate river floodplains

Floodplain inundation is considered as crucial for the recruitment of fish in lowland rivers, by either providing suitable spawning areas as well as breeding habitats for young-of-the-year fish (YOY), as well as for supporting species that exhibit different life history-strategies in order to be differently adapted to long term discharge patterns. Fish communities in a set of 38 waterbodies on the Lower Rhine floodplain, representing different long-term frequencies of inundation and differently affected by seasonal inundations, were sampled by means of electro fishing (point abundance sampling, total n = 42,701 points) over a four-year period in order to identify species-specific and life-history strategy related patterns of spatio-temporal floodplain habitat utilisation. For 18 species (total catch: n = 107,150), typically occurring in European lowland rivers and representing different ecological guilds, different responses towards seasonal inundations were found. YOY of most species closely associated to the periodic strategy (e.g., Abramis brama, Aspius aspius, Blicca bjoerkna) were highly abundant in frequently inundated waterbodies, provided these were subject to inundations occurring in spring and early summer and coincided with temperatures required for spawning. However, recruitment in these species was impaired or failed when no inundations in this time frame occurred, although adults were present. In contrast, most species associated to the opportunistic strategy (e.g., Gasterosteus aculeatus, Pseudorasbora parva, Leucaspius delineatus) had highest recruitment in waterbodies unaffected by inundations in this time frame, which had detrimental effects on these predominantly small sized species. Spatio-temporal floodplain habitat utilisation of YOY fish (most rheophilic species as well as eurytopics) is suggested to be size-related, since most fast growing periodic strategists left the floodplain at given connectivity at latest in winter and were then absent in the subsequent year. Smaller YOY fishes and all opportunistic species either remained in more isolated waterbodies, or dispersed from there across the floodplain to some degree during extensive winter floods. These findings suggest adaptations to the long-term hydrograph of large river systems, with flood-related recruitment patterns predominantly occurring in periodic strategists and low-flow recruitment strategies in opportunistic strategists and stagnophilic species. The results of this study point to the significance of hydrological transversal floodplain gradients that provide diverse communities and population maintenance of different life-history strategies, evidencing that fish communities within the floodplain act as indicators for the hydrological conditions.     

Characteristics of cladoceran and copepod communities in floodplain habitats of the Atchafalaya River Basin

In the summer of 1994, floodplain habitats of the Atchafalaya River Basin were surveyed for cladocera and copepoda. Collection sites were grouped into three distinct habitat types (black-water, brown-water and green-water) based on a principal components analysis of five hydrographic variables (current velocity, Secchi disk depth, surface percent saturation of dissolved oxygen, dissolved oxygen differential and surface water temperature). An ANOVA of four community indices (total abundance, Shannon–Weiner diversity (H'), richness, and evenness) was performed on both cladoceran and copepod communities among the three floodplain habitats. Common species were compared among habitats (² goodness-of-fit) to determine where they were most abundant. Green-water habitats had the greatest overall abundance of cladocerans and copepods (dominated by Diaphanosoma birgei, Moina micrura and Mesocyclops edax), but ranked lower in diversity and evenness than black-water and brown-water habitats where Ilyocryptus spinifer, Simocephalus serrulatus, Macrocyclops albidus (black-water) and Bosmina longirostris and Acanthocyclops vernalis (brown-water) were most abundant, respectively. These results indicate that the mosaic of floodplain habitats within large temperate river systems support unique zooplankton communities, and that these habitats are largely a function of seasonal hydrographic features.     

Aquatic macrophytes diversity in lagoons of a tropical floodplain: The role of connectivity and water level

Abstract The goal of this research is to evaluate how the assemblages of aquatic macrophytes in marginal floodplain habitats, with different degrees of connectivity to the main river, respond to water level fluctuations. Samples were carried out quarterly (May 2000 to March 2002) in seven lagoons of the Upper Paraná River floodplain (22°30′ and 22°45′‐S and 53°15′ and 53°30′‐W) with different degrees of connectivity (connected and disconnected to the main river). In each lagoon, a shore‐pelagic zone transect was marked and at every 2 m the depth and the cover of each aquatic macrophyte species were recorded (Domin‐Krajina scale) in a quadrat of 0.25 m². A total of 29 aquatic macrophyte species and an unusual decrease in water level were recorded in August 2001. Drawdown had a negative impact on species richness, only in connected lagoons, which was shown by a positive relationship between depth and species number (r‐Spearman = 0.86; P < 0.01). Depth affected Beta diversity positively (r‐Spearman = 0.79; P < 0.05). Drawdown affected the connected and disconnected lagoons differently, which can be attributed to their different morphometry. In this period, ‘habitat contraction’ was higher on connected lagoons. Positive correlation between mean species number and depth, and between beta diversity and depth, are factors that support this affirmation. Indicator species analysis showed that for disconnected lagoons, Oxycaryum cubense (Cyperaceae), Polygonum meissnerianum (Polygonaceae) and P. ferrugineum, with indicator values (IndVal) of 53, 30 and 25%, respectively, were indicator species. Salvinia spp. (Salvinaceae) (62%), P. acuminatum (44%) and the Ricciaceae Ricciocarpus natans (0%) were the indicator species of the connected lagoons.     

中国菱属(菱科)植物的分类研究

菱科(Trapaceae)仅菱属(Trapa L.)1属,该属是典型的水生多型植物,中国乃至全球以往的分类处理分歧很大。基于文献查阅、野外采集、标本鉴定和栽培观察,对菱属植物分类的主要形态性状作了系统评价。果体大小和果冠变异稳定,可以用于属内种的划分,果喙大小和角的数目则可以用于种下变种的划分。在此基础上,对中国菱属作了分类处理,承认了细果野菱(T. incisa)和欧菱(T. natans)2个种,并将欧菱划分为6个变种,对其中4个变种作了新的组合。将10个种名和12个变种名处理为异名,并对5个名称(Trapa amurensis,T. bispinosa,T. dimorphocarpa,T. japonica,T. manchurica)作了后选模式标定。     

Does Invasion of Exotic Plants Promote Invasion of Exotic Flower Visitors? A Case Study from the Temperate Forests of the Southern Andes

Habitat disturbance, particularly of human origin, promotes the invasion of exotic plants, which in turn might foster the invasion of alien-interacting animals. Here we assess whether the invasion of exotic plants – mostly mediated by habitat disturbance – facilitates the invasion of exotic flower visitors in temperate forests of the southern Andes, Argentina. We recorded visit frequencies and the identity of visitors to the flowers of 15 native and 15 exotic plant species occurring in different highly disturbed and less disturbed habitats. We identified three alien flower visitors, the hymenopterans Apis mellifera, Bombus ruderatus, and Vespula germanica. We found significantly more visitation by exotic insects in disturbed habitats. This pattern was explained, at least in part, by the association between alien flower visitors and flowers of exotic plants, which occurred more frequently in disturbed habitats. However, this general pattern masked different responses between the two main alien flower visitors. Apis mellifera exploited almost exclusively the flowers of a subset of herbaceous exotic plants that thrive under disturbance, whereas B. ruderatus visited equally flowers of both exotic and native plants in both disturbed and undisturbed habitats. We did not find any strong evidence that flowers of exotic plants were more generalist than those of native plants, or that exotic flower visitors were more generalist than their native counterparts. Our results suggest that alien plant species could facilitate the invasion of at least some exotic flower visitors to disturbed habitats. Because flowering plants as well as flower visitors benefit from this mutualism, this association may enhance, through a positive feedback, successful establishment of both exotic partners.     

Effects of invasive species on plant communities: an example using submersed aquatic plants at the regional scale

Submersed aquatic plants have a key role in maintaining functioning aquatic ecosystems through their effects on the hydrological regime, sedimentation, nutrient cycling and habitat of associated fauna. Modifications of aquatic plant communities, for example through the introduction of invasive species, can alter these functions. In the Sacramento-San Joaquin River Delta, California, a major invasive submersed plant, Brazilian waterweed Egeria densa, has become widespread and greatly affected the functionality of the submersed aquatic plant community. Rapid assessments of the distribution and abundance of this species are therefore crucial to direct management actions early in the season. Given the E. densa bimodal growth pattern (late spring and fall growth peaks), summer assessments of this species may indicate which and where other submersed species may occur and fall assessments may indicate where this and other species may occur in the following spring, primarily because the Delta’s winter water temperatures are usually insufficient to kill submersed aquatic plant species. We assessed community composition and distribution in the fall of 2007 and summer of 2008 using geostatistical analysis; and measured summer biomass, temperature, pH, salinity, and turbidity. In the fall of 2007, submersed aquatic plants covered a much higher proportion of the waterways (60.7%) than in the summer of 2008 (37.4%), with a significant overlap between the seasonal distribution of native and non-native species. Most patches were monospecific, and multispecies patches had significantly higher dominance by E. densa, co-occurring especially with Ceratophyllum demersum. As species richness of non-natives increased there was a significant decrease in richness of natives, and of native biomass. Sustained E. densa summer biomass negatively affected the likelihood of presence of Myriophyllum spicatum, Potamogeton crispus, and Elodea canadensis but not their biomass within patches. Depth, temperature and salinity were associated with biomass; however, the direction of the effect was species specific. Our results suggest that despite native and invasive non-native submersed plant species sharing available niches in the Delta, E. densa affects aquatic plant community structure and composition by facilitating persistence of some species and reducing the likelihood of establishment of other species. Successful management of this species may therefore facilitate shifts in existing non-native or native plant species.     

Germination of Epiphytic Bromeliads in Forests and Coffee Plantations: Microclimate and Substrate Effects

This study explores whether differences in germination ability shape habitat distributions among closely related epiphytic species, particularly in the context of the ability to colonize disturbed habitats. We compared the germination of three epiphytic bromeliad species differing in their ability to colonize secondary arboreal vegetation in natural forests, and in old and young coffee plantations. We asked if germination is related to their distribution within the canopy and between habitats, and the extent to which the substrate (branch) or microclimate affects germination success. Tillandsia viridiflora, a species that is largely restricted to closed forests, had highest germination success in natural forests, Tillandsia juncea, a pioneer species, germinated best in young coffee plantations, and Tillandsia heterophylla, an intermediate species, equally in forests and young plantations. Surprisingly germination rates of all three species were lowest in old plantations. Bryophyte cover on branches had a positive effect on germination of T. viridiflora and T. heterophylla, but T. juncea germination rates were largely independent of climate and substrate. These results show that germination can limit the ability of species to colonize disturbed habitats and also contributes to within‐canopy distribution. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

Biology of the rainbowfish,Glossolepis multisquamatus (Melanotaeniidae), from the Sepik River floodplains,Papua New Guinea

Synopsis G. multisquamatus is abundant in the Sepik River, preferring floodplain lakes and marginal areas of floodplain with moderate turbidity. It is the only rainbowfish documented to inhabit river floodplains. Migrations onto and off the floodplain occur in response to changes in flood conditions. Seasonality is evident in reproduction, condition factor and fat deposit and stomach fullness indices; all increasing in the flood season. Fecundity is high compared with stream dwelling rainbowfish species mainly due to decreased egg size. The reproductive strategy ofG. multisquamatus is interpreted as a response to increased adult mortalities encountered on floodplains in comparison to more stable stream habitats occupied by related species.G. multisquamatus is carnivorous, its diet being similar to other rainbowfishes, consisting of a variety of small invertebrates taken from mid-water or the water surface. The ecology and behaviour ofG. multisquamatus is explained as a partial colonisation of newly developed floodplains in this river.